The invention pertains to an apparatus for centrifugal casting under vacuum, in particular for the production of castings made of titanium aluminides.
RU 2 056 971 C1 as well as GB 647 019 A describe centrifugal casting machines having an auxiliary acceleration device for generating a force to overcome a moment of inertia of a rotor. However, both machines are not suitable for carrying out a centrifugal casting process under vacuum.
US 2001/0045267 A1 describes an apparatus for centrifugal casting under vacuum. In the known apparatus a first crucible and a rotor are accommodated within a gas-tight vacuum chamber. A melt being taken up in a first crucible is poured into a second crucible or gate, respectively, which is part of the rotor which can be rotated around a vertical axis. The gate has a plurality of radial outlet openings opposite of which there are arranged inlet openings of molds extending in a radial direction. The melt being poured into the gate is forced by centrifugal forces through the outlet openings thereof into the molds. By use of this apparatus castings with a simple geometrical shape like valves for internal combustion engines and the like can be produced.
However, when producing castings from titanium aluminides or titanium grade 2 having thin walls and a complex geometry, e.g. shrouded turbine blades or turbo charges wheels, one is encountered with several problems, like the formation cold-runs, hot tears, shrinkholes, pores, voids and the like.